Toxic and Hazardous Waste
Toxic and Hazardous Waste waste materials that are harmful to health, may cause physical injuries, and damage the environment to the detriment of the biotic balance in the ecosystem. Human activities often result in the generation of many toxic and hazardous wastes. The type and quantity of such wastes depend on many factors such as the socio-economic condition of the country, level of industrialisation and cultural and anthropological attributes of the people. The source of such wastes can also be varied-home, business, industry, transportation, and agriculture. Production of such wastes from domestic sources mainly consists of broken glass, cans, sharp metal objects, organic substances such as paints, etc. Generally similar types of wastes are produced by business establishments - restaurants and service outlets such as gasoline stations and mechanical workshops, hospitals and clinics. It is the industry that generates the bulk of the toxic and hazardous wastes, and to a lesser extent agriculture, where extensive use of insecticides and other pesticides may cause accumulation of these substances in soil and water to levels that may be dangerous to human health.
Production of toxic and hazardous wastes from domestic and business sources in Bangladesh may be varied in type but its quantity is not very large mainly because the socio-economic conditions of the people do not allow extensive use of organic solvents, household insecticides etc and things such as glass bottles and metal objects are usually recycled. Automobile service stations, however, produce large quantities of discarded engine lubricating oil (locally called 'mobil' in a generic sense) which is collected and some amount of it is said to be re-used after applying some improvised technology. The substance is thus recycled to produce in turn other types of toxic material of not too well-known applications which is indeed a matter of great concern; although at the present time direct release of automobile discards into the environment may not pose a significant threat.
Hazardous wastes generated from industrial sources are of varied types depending on the nature of the industry. In general, the food industries usually are poor contributors to toxic waste generation, so also are the pharmaceutical industries because these industries mainly carry out packaging of imported drugs and have thus little scope to generate much toxic waste. Industrial units in manufacturing sector span over a few areas such as textiles, tannery, fertiliser, cement etc. Most of these industries discharge waste into the river after some treatment as required by the regulatory agencies but regulatory rules are not strictly followed or monitored. There are about 250 tanneries in the Hazaribag area of Dhaka city where millions of pieces of hides are processed and most of the toxic chemicals used in the processing are discharged into the river largely untreated.
Radioactive waste is a major hazardous material whose adverse effects can only be reduced through the natural process of radioactive decay. The decay process cannot be enhanced by any technology known to man. Thus, safe storage for a certain length of time during which the level of radioactivity will reach a safe limit, is the routine method of disposal of radioactive waste. In Bangladesh, the use of radioactive material is limited to scientific research carried out in a small number of institutions where mainly 32P is used and to some clinical applications where 131I is used to treat hyperthyroidism at the nine centres of Nuclear Medicine located in different cities and operated by the bangladesh atomic energy commission (BAEC). The BAEC is also responsible for granting licence to users of radioactive material and monitoring its safe use and for proper pre-disposal storage of radioactive waste. When the radioactivity in the waste reaches the recommended safe level, it is usually discharged into the normal sewage system. [Zia Uddin Ahmed]